In order to efficiently use space, which may be at a premium, equipment is often designed to fit within available space, which may be a pocket type compartment i.e. a compartment with only one open side in which to insert the equipment. As a result there is usually very little clearance between the equipment being mounted and the surrounding equipment or housing to either place and secure a fastener.
One of the ways of mounting a device in a pocket type compartment is through the use of dagger pins that are mounted in the bottom of the pocket type compartment and dagger plates which are mounted on the device. The dagger pins coact with the dagger plates to constrain the article from movement in two mutually perpendicular directions but allow movement in a third axis which is parallel to a central axis of the dagger pins, thus allowing the dagger plate to be slid onto the dagger pins.
Briefly, the dagger pin mounting allows one to blind mount the device in a pocket type compartment by first sliding one end of the device into the pocket compartment until the dagger plates on the equipment engage the dagger pins in the compartment. Next, one can secure an exposed end of the device to a support housing by conventional fasteners.
By having a dagger plate on the end of the device that is inserted in a pocket type recess and mounting a dagger pin in the pocket one can blind mount the device on a dagger pin without the need to have a hand or tool access space to secure a fastener. That is, the dagger plate can be slid into engagement around the dagger pin without having to actually see either the dagger pin or the dagger plate. Once in engagement the dagger pin and the dagger plate coact without further action to restrict the device from lateral movement.
The other end of the device is then retained by extending a fastener through the device and into the support housing at an angle which is generally perpendicular to the axis of the dagger pin to prevent the device from moving out of the pocket compartment.
The use of dagger pins that restrain motion in two mutually perpendicular axis in conjunction with a second mount that restrains the movement of the device in the third mutuality perpendicular axis ensures that the device can be maintained in a fixed condition on the support housing. However; dagger pin mounts are undesirable in high vibration environments, because the necessary alignment clearances between the dagger pin and the dagger plate allows the device to swing and impact on the dagger pin generating amplified loads on the device.
As a result, dagger plate mounting requires one to compensate for potential misalignment of the dagger pins in the compartment and the dagger plates on the device. The alignment compensation techniques used, namely, forming a dagger pin hole in the dagger plate that is larger than the dagger pin can lead to high vibration input to the device causing premature device failure. More specifically, an elongated slot is formed in the dagger plate for engagement with a round dagger pin, which leaves a “free spacing” between the dagger pin and the dagger pin hole in the dagger plate.
The problem of vibration failure of a device secured by dagger plate and a dagger pin is accelerated if the alignment compensation techniques involves “free spacing” with only one of a set of dagger pins is provided with a smaller diameter than the diameter of the alignment holes in order to make it easier to align and position the device on the dagger pins. For example, a small diameter difference between the dagger pin and the sidewalls of the hole in the dagger plate can quickly lead to device failure as the article is free to vibrate laterally before being stopped by the contact of the cylindrical surface of the dagger pin with the sidewall of the alignment hole. Unfortunately, it is virtually impossible to provide for effective blind mounting unless one maintains at least some free spacing between the dagger plates on the device and the dagger pins, which is done by making at least one of the holes in the dagger plate substantially larger than the dagger pin. The result is the device soon begins to vibrate at its natural frequency, which hastens system failure.
In addition to devices being mounted in a tight or cramped space the device might also be positioned behind other devices, which requires removing other devices in order to replace the device if it should fail. Thus, there is a need to mount a device in a tight or cramped space in a protected conditions so that the device can be maintained therein with infrequent need for servicing. Consequently, the device needs to be isolated from the support housing to inhibit vibrations that can cause premature failure of the device.
Generally, vibration isolation is achieved with some type of elastomer positioned between the device and the support housing in order to damp vibrations. Unfortunately, conventional dagger pin mountings provide rigid contact between the dagger pin, the dagger plate and the article.
The present invention provides a mounting system that permits an article to mounted in a tight cramped space using a dagger plate and a dagger pin while at the same time providing a vibration isolation mount.